The goal of the present research is to demonstrate the importance of sequential effects when performing the computationally demanding task of reaching around obstacles. Results from a preliminary experiment showed significant sequential effects in obstacle avoidance. Specifically, when obstacle-present and non-obstacle trials were intermixed within a block of reaching trials, the handpaths in the non-obstacle trials were more curved than were handpaths from participants who performed the same movements when no obstacle was ever present. This sequential effect, called the obstacle-perseveration (OP) effect, is thought to be due to the perceptual-motor system's inability to switch from performing obstacle-avoiding movements to non-obstacle-avoiding movements under some conditions. In three proposed experiments, the time between trials, obstacle size, and number of possible target locations will be manipulated. Manipulation of these variables will be performed to obtain further behavioral data that will help identify the source(s) of the OP effect. Such information will not only shed light on the control of obstacle-avoidance behavior; it will also lead to a better understanding of how the perceptual-motor system operates in general.